In different applications, it can be worthwhile to determine the power of an analog AC voltage signal (AC signal) as an input signal over a wide dynamic range as a digital value. Different techniques are known for this, such as peak value detection or a limiting amplifier, for example. However, such techniques have the disadvantage that they do not determine an effective value, such as the root mean square (RMS), for example. Therefore, such techniques can particularly have a dependency on a modulation technique for the AC signal and/or a dependency on a ratio between peak power and mean value, for example as described by crest factor.
In order to determine the RMS value, techniques can square the AC signal and then use a logarithmic analog amplifier to translate it into the analog domain. Subsequently, analog-to-digital (AD) conversion by means of an analog-to-digital converter (ADC) can take place in order to obtain a digital output signal. By way of example, this can be done using an ADC that is operated in accordance with the successive approximation method; such an ADC is frequently also referred to as a successive approximation ADC (SAR-ADC).
However, techniques for determining the RMS value have the disadvantage that the logarithmic amplification in the analog domain by means of the analog amplifier means that there can be a significant dependency on constraints, such as process tolerances, temperature and the supply voltage, for example. The output signal can then be accordingly distorted. Thus, an accuracy of the AD conversion can decrease.